The proposed study concerns the regulation of phosvitin messenger ribonucleic acid (M-RNA) synthesis by estrogenic hormones. The synthesis of phosvitin is initiated in the livers of male and female birds by estrogens. The initiation of the synthesis of the M-RNA for this phosphorprotein is presumably brought about through the participation of the estradiol-receptor complex present in liver nuclei. The initial aim of this study is to isolate, identify, and purify the the M-RNA for phosvitin. The purified M-RNA will be used as template for the synthesis of complimentary deoxyribonucleic acid (cDNA) by the RNA instructed DNA polymerase of avian myeloblastosis virons. This cDNA will be used as a hybridization probe to study the kinetics of phosvitin M-RNA synthesis in the livers of estrogen treated roosters. Subsequent studies will be directed toward the molecular role of the estradiol-receptor complex in the induction of this M-RNA.